The invention relates to a method of influencing ink-trapping behavior of ink-conducting components of a printing unit in a rotary printing press, and a device for implementing the method.
German Patent 23 03 718 which exemplifies the state of the art discloses an ink-supplying arrangement for a printing press, and a method of supplying a rotating printing plate with printing ink. For the purpose of reducing shock in the inking unit and for eliminating slurring in the printed image, a friction drive is provided between rollers of the inking unit, as well as an over-running clutch which engages or becomes active when the speed of the drive is lower than a given working speed.
The published German Patent Document DE 28 08 856 C2 discloses an inking-unit drive for a rotary printing press. Provided with this inking-unit drive is a vibrator roller which is disposed between an ink-duct roller and a first ink-transfer roller, and the drive for the entire inking unit results via gearwheels from drive gears of the plate cylinder and/or the blanket cylinder. A drive gear of a lower ink-transfer roller is directly connected to a main drive shaft, whereas all of the remaining driven inking-unit rollers are connected with a drive gear of the plate cylinder.
The published German Patent Document DE 18 40 458 A1 discloses a printing press have printing-unit cylinders which are movable forwards in an inching mode for mounting or locking the printing plates. With this construction, it is possible to avoid shocks of a form roller drivable by an adjacent printing-unit cylinder from acting upon the drive elements, by providing a clutch in the vicinity of the gear train connecting the form roller to the adjacent printing-unit cylinder, the clutch being automatically disengageable for operating in the inching mode.
Rotary printing presses equipped with units for the direct imaging of the printing forms within the printing units have proven that heating of the printing-form cylinder and the inking unit has extremely undesirable consequences. If the temperature of the printing form or the inking unit is too high as a result of thermal conduction or other forms of heat transfer, the printing form tends to scum, and the ink-trapping behavior thereof deteriorates due to the temperature being too high and due to premature vaporization or evaporation of dampening medium, thus causing a delay in the direct transition into the production printing run.
It is accordingly an object of the invention to provide a method and device for influencing ink-trapping behavior which are improved over the prior art particularly in printing presses having units for the direct imaging of printing forms within the respective press during the start-up phase.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method of influencing ink-trapping behavior of ink-conducting components of a printing unit in a rotary printing press, which comprises disconnecting at a clutch location an inking-unit drive coming from printing-unit cylinders; directly imaging a printing form on a printing-form cylinder within the rotary printing press; and reestablishing the drive connection between the inking unit and the printing-unit cylinders at the clutch location after completing the direct imaging of the printing form.
In accordance with another aspect of the invention, there is provided, in a rotary printing press, a device for performing a method of influencing ink-trapping behavior of ink-conducting components of a printing unit, comprising a clutch system disconnectably connecting at a clutch location an inking-unit drive coming from printing-unit cylinders of the printing unit, the clutch system including an axially acting clutch.
In accordance with another feature of the invention, the clutch is of a type actuatable by a pressure medium.
In accordance with an alternative feature of the invention, the clutch is an electromagnetically actuatable clutch.
In accordance with a further feature of the invention, the clutch is disposed on a shaft of a distributor roller.
In accordance with an alternative feature of the invention, the clutch is disposed on a control shaft.
In accordance with a concomitant alternative feature of the invention, the clutch is mounted on a journal of a printing-unit cylinder.
In the performance of the method steps mentioned hereinbefore, assurance is offered that the temperature of the printing form is kept constant, without any excessive vaporization which would otherwise falsify the set dampening-medium ratio, and with the production of a considerably smaller number of waste copies prior to starting the production run, because the ink-trapping properties of the printing form eliminate scumming. This considerably improves the productivity of a printing press which is equipped accordingly.
In a device for performing the method according to the invention, a clutch system at a clutch location includes a clutch operatable in axial direction and subjected to a pressure medium, by means of which the inking unit is disconnectable from the drive. Instead of a clutch to which a pressure medium is applied, it is conceivable to provide an electromagnetically actuated clutch. The respective clutch is disposed on a shaft of a distributor roller or drum. Alternatively, the respective clutch is mounted on a transmission shaft, i.e., a control shaft.
Another alternative mounting location for the clutch is the journal of the respective printing-unit cylinder.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and device for influencing ink-trapping behavior, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.